Traffic Light Helps Make Healthy Decisions

Wandering the aisles of the local grocery store, you are faced with hundreds — if not thousands — of decisions.

What food is best for the family? How do I balance nutritional needs with taste with the budget?

Reading food labels is one way to help make those decisions, but they are often in tiny print and contain ingredients you never heard of.

Two recent studies show that putting a traffic light on packages — green for healthy, red for unhealthy and yellow for neutral — helps shoppers choose the most nutritious foods.

In fact, the traffic lights actually increase our sensitivity to making the healthiest choice, according a recent brain imaging study.

In the first study, researchers at the University of Bonn in Germany found that a traffic light label is more effective in helping consumers resist high-calorie foods than a purely information-based label.

They reached that conclusion after observing study participants in a brain scanner as they made purchase decisions.

The traffic signal labels are supposed to be an easy-to-understand indication of the overall “healthiness” of a food. For example, “red” symbolizes a high percentage of fat, sugar or salt, “green” a lower percentage. Just as on an actual traffic light, yellow falls in the middle.

For this first study, 35 adults, including 19 women, were shown 100 products and their nutritional information while they were lying in the brain scanner. Products ranged from chocolate to yogurt.

Nutritional information was shown either in the form of traditional nutrition labels with grams and percentages per portion or in the form of a traffic light, explained Dr. Bernd Weber of the Center for Economics and Neuroscience (CENs) at the University of Bonn.

Laura Enax and Bernd Weber from the University of Bonn with various products from which subjects should choose. Photo by:Rolf Müller/UKB-Ukom

The study participants then had to indicate how much they were willing to pay for a particular product.

What the researchers discovered was that the participants were willing to pay significantly more money for the same product when the traffic light label was green compared to an information-based label.

However, if the label was red, the willingness to pay decreased more compared to the conventional information.

“You can conclude that the traffic light label acts as a reinforcer: The health relevance of the ingredients is weighed more heavily into purchasing decisions compared to simple nutrition information,” said Laura Enax of CENs.

While the study participants were thinking about what price they wanted to pay for a particular product, the scientists recorded the activity of various brain regions using functional magnetic resonance imaging.

What they discovered is that a red traffic light label activated a structure in the left inferior frontal gyrus, which has been repeatedly shown to be important for self-control.

Activity in this region influenced the ventromedial prefrontal cortex, a region that “calculates” the subjective value of a product via the reward system, leading to decreased willingness to pay for unhealthy products, the researchers explain.

“The traffic light label appears to enable the study participants to better resist unhealthy foods compared to a label containing the traditional information on grams and percentages of the particular ingredients,” Weber said. “A traffic light label probably implicitly increases the weight consumers place on healthiness in their decision.”

The German scientists took the experiment one step further. Working with researchers at The Ohio State University, they set out to investigate whether information about food components can convince consumers to reach for foods with fewer calories.

For this experiment, 44 adults were first asked to what extent they like 100 different foods. Half of the products — including chips, chocolate bars and cookies — were less healthy foods. The other half were healthier, such as rice waffles and natural yogurt.

The participants were not allowed to eat anything for four hours before the actual test so that everyone completed the study with the same size of appetite, the researchers noted.

On a computer screen, the participants were able to choose from two products, one healthy and one less so. In some cases, the nutritional information was presented in the form of a traditional food label, in grams and percentages.

In other cases, this information was combined with a food traffic light, with red symbolizing a high proportion of fats, sugar or salt, while green represented a low proportion. Yellow held a middle position.

When assessing the data, the scientists also took into account the personal preferences of the participants: Is the product among the person’s favorite foods or did they not like the taste very much?

What the researchers discovered is that the participants were guided — above all else — by their taste when the nutritional information shown consisted of grams and percentages.

“However, if this information was combined with the food traffic light colors, health aspects of the product played a greater role,” said Enax.

On average, it was several percentage points more likely that healthier foods were chosen when the traffic light colors came into play than when just figures were shown on the food packaging, she noted.

The researchers also tested whether participants were influenced when a label featured a green or red label for just one ingredient.

“The effects here are much smaller compared with the full nutrient traffic light,” Enax reported.

In the first study, the scientists showed that the traffic light acts like an “amplifier” to areas of the consumers’ brains responsible for self-control, Weber noted.

“The current study was about how a better balance can be achieved between taste-related preferences and health aspects when making a purchase,” Weber said. “The traffic light colors seem to have a much more favorable effect here than pure percentages and grams.”

What do you think? Would a traffic light help you make decisions about what foods to put in your grocery cart?